1. Field of the Invention
The present invention relates to a machine for bending metal to form the outside skins of channel letters. More particularly, the present invention relates to a machine that can automatically bend metal material into the form of outside skins of channel letters for signs, primarily exterior signs.
2. State of the Prior Art
At most shopping strip malls, restaurants and other stores, the main electrically illuminated sign which is out front, typically displaying the name of the business, will be made of channel letters. Each channel letter is composed of a front face that is usually made of plastic, and can be any of various colors. The front face forms the letter seen by the public in viewing the sign. Each channel letter also has a back, which is commonly made of aluminum. The front face and back can be cut manually or by using computer controlled routers. Between the front and the back, however, there is an outside skin, usually made of metal, connecting the front face and the back.
The outside skin is usually made of metal. The outside skin has to be formed into the shape of the letter matches the same shape of the cut out front face and back. To date, all of the metal outside skins of channel letters are manually bent. This is a very labor intensive job, and for this reason channel letters make up the highest dollar segment of the multi-billion dollar sign industry.
Various apparatus are known in the prior art for bending sheet or sheet-like material. U.S. Pat. No. 5,461,893 discloses a method and apparatus for bending steel rule in which a coil of steel rule material is unwound and fed to a notcher/cutter that cuts notches in the rule at selected locations prior to bending. The rule is then bent by a clamping device holding the rule and a bending tool rotating to bend the rule. The bending tool can be positioned on either side of the rule for making bends in opposite directions. U.S. Pat. Nos. 4,773,284 and 3,823,749 provide bending devices that are similar in operation.
U.S. Pat. Nos. 5,463,890, 5,507,168 and 5,495,741 each disclose a bending mechanism that operates slightly differently from that above. In each of these patents, a strip of material is passed through a clamping or holding portion, and a bending portion can be relatively rotated in either rotary direction to cause the bend of the material to occur.
U.S. Pat. Nos. 3,879,979, 3,986,470, 3,038,252, 3,270,541 and 3,581,535 disclose various methods of bending metal materials also including in some instances the formation of notches in the material.
However, none of the above-disclosed apparatus and methods for bending metal materials are suitable for forming the outside skins of channel letters. In particular, none of these devices can automatically form a channel letter.